JPH0125186B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission electron detection device for a transmission scanning electron microscope.

FIG. 1 shows the schematic structure of a conventional transmission scanning electron microscope. In this type of electron microscope, a field emission type electron gun is used for the purpose of narrowly focusing an electron beam and projecting it onto a sample. A first anode 3 facing the field emission cathode 1,
When a voltage (~3KV) is applied from the extraction voltage source 2, electrons are emitted from the field emission cathode 1. These electrons are accelerated to an arbitrary voltage (50 to 100 KV) by an accelerating voltage source 4 applied to the second anode 5.

The electrons accelerated as described above pass through the focusing lens 6
As a result, an electron beam is narrowly focused on the surface of the sample 8, and the surface is scanned by the deflection coil 7.

Since the sample 8 is generally thin, about 1000 Å, most of the electrons will pass through the sample. Since the intensity and scattering angle of the electron beam that has passed through the sample differ depending on the local state, thickness, and type of atoms of the sample, it is possible to provide internal information about the sample correspondingly.

In order to obtain internal information about a sample in this way, a transmission scanning electron microscope uses a bright field detector 22 to detect electrons that have passed through the sample without being scattered, and a dark field detector 21 to detect scattered electrons. It is used.

The signal obtained by the bright-field detector 22 or the dark-field detector 21 is selected by a switch 16 and then amplified by an amplifier 17.The signal obtained by the bright field detector 22 or the dark field detector 21 is amplified by an amplifier 17. The brightness is modulated, and an image of the sample 8 is formed. If two cathode ray tubes 19 are used, it is possible to simultaneously form bright-field and dark-field images.

The dark field detector 21 has a fluorescent surface 10 as a light emitter.
The electrons that have passed through without being scattered by the sample are passed through the hole 20 downwards, and the scattered electrons are used as a fluorescent light emitter. The light is converted into light by the surface 10 and guided to the photomultiplier tube 11 by the light guide 9 as a light transmitter.

FIG. 2 is a plan view of the tip of the dark field detector 21 viewed from above. In order to align the center of the circular hole 20 and the electron beam, the dark field detector 21 can be moved horizontally. On the other hand, electrons passing through the circular hole 20 in the center of the dark field detector 21 excite the fluorescent surface 13, are converted into light, and are guided to the photomultiplier tube 15 by the light guide 14 as a light transmitter.

In addition, as shown in FIG. 1, the bright field detector 22 is provided with:
A diaphragm 31 with a small circular hole 30 is provided to further restrict the electrons passing through the circular hole 20. This aperture 31 is configured so that it can be moved horizontally on a plane perpendicular to the optical axis.
Axis alignment adjustment is possible. Further, by adjusting the diameter of the circular hole 30, it is possible to change the contrast of the bright field transmitted image.

In this way, conventional transmission scanning electron microscopes allow alignment, contrast adjustment, etc.
Although a high-performance device can be realized, since the movable adjustment portion is disposed within the vacuum-maintained casing 32, the structure is complicated and adjustment handling is not easy.

The present invention solves the above-mentioned difficulties in conventionally used transmission scanning electron microscopes, and provides an apparatus that maintains the conventional high performance, is simple in construction, and is easy to handle and adjust.

FIG. 3 shows an embodiment of the present invention.
The electrons transmitted through the sample 8 and scattered excites the fluorescent surface 27, which serves as a light emitter, disposed within the housing 32, and emits light. This light passes through, for example, a fiber plate 23 constituting a light transmitting body and is displayed as a light image on the opposite surface.

That is, in this case, a transmitted optical image corresponding to the internal information of the sample 8 is displayed on the lower surface of the fiber plate 23 as a light transmitting body. A detection means 26 such as a photomultiplier tube is arranged on the lower surface of the fiber plate 23 to detect the optical signal after converting it into an electric signal.In between, a dark field shielding plate 24 shown in FIG. 4A is inserted to detect the bright field. image is obtained and the fourth
A dark-field image can be obtained by inserting the bright-field light shielding plate 25 shown in FIG.

The dark-field light-shielding plate 24 blocks the dark-field image electrons 29a shown in FIG. 3, and allows only the bright-field image electrons 29b to pass through its center hole 28, thereby inputting the light to the photodetecting means 26 such as a photomultiplier tube. By giving an electrical signal corresponding to the internal information of the sample 8, it is possible to obtain a transmitted image of the sample using, for example, a cathode ray tube display. Furthermore, by changing the diameter of the center hole 28 of the dark-field light-shielding plate 24, it can also function as the circular hole 20 for the aperture shown in FIG.

In addition, if two polarizing plates are used as light shielding plates, 1
It is possible to switch between bright field and dark field by simply rotating the polarizing plates. Figure 5 shows an example of this. In the figure, 34 in A is a fixed first polarizing plate, and the polarization direction is set in the center of this plate.
A disk 35 rotated by 90 degrees is inserted. 33
is a second polarizing plate having the same polarization direction as the disc 35, and if stacked as is, only the disc 35 will pass light,
A bright-field image is obtained, and when the second polarizing plate 33 is rotated by 90 degrees, a dark-field image that passes through other than the disk 35 is obtained.

Further, FIG. 6 shows another embodiment of the light shielding plate. In the figure, 36 is a transparent photographic film section, and a light-shielding section 37 is provided in the center of the photographic film by blackening the photographic film or pasting black paper or a metal mask on that section only. . The bright field image electron 29b shown in FIG.
The bright field optical image generated at step 7 is blocked by the light shielding section 37 shown in FIG.
However, only the dark field optical image generated on the fluorescent surface 27,
A photoelectric conversion detector 26 can be provided as an input.

In the above-described transmission scanning electron microscope according to the present invention, the input surface of the light transmitting member to the light detection means 26 is installed outside the housing 32, so the transmitted optical image of the input surface is It is possible to see directly
The axis of the electron optical system can be adjusted while monitoring the transmitted optical image. Further, scanning of the electron beam is stopped at a predetermined position on the sample surface, and an electron diffraction image of the sample is obtained on the input surface of the photodetecting means 26 via the light transmitting body, and the film is removed as necessary. It is also possible to easily photograph the object in close contact with the object.

As explained above in detail, the transmission scanning electron microscope according to the present invention can switch between dark-field transmitted images and bright-field transmitted images, and perform electronic Since it is possible to provide a device that can realize axis adjustment of an optical image system, contrast adjustment, and photographing of an electron diffraction image, its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventionally used transmission scanning electron microscope, FIG. 2 is a plan view of a conventionally used bright field detector, and FIG. 3 is a transmission electron microscope according to the present invention. FIG. 4 is a partial configuration diagram of a first example of a light shielding plate for a transmission electron microscope according to the present invention.
FIG. 5 shows a second example of a light shielding plate for a transmission electron microscope according to the present invention, and FIG. 6 shows a third example of a light shielding plate for a transmission electron microscope according to the present invention. Explanation of symbols, 8... Sample, 23... Fiber plate, 24... Dark field light shielding plate, 25... Bright field light shielding plate, 26... Photoelectric conversion detector, 27... Fluorescent surface, 28... Center hole, 29a... dark field image electron, 29b... bright field image electron, 33... second polarizing plate, 34... first polarizing plate, 35... disk, 3
6... Photographic film section, 37... Light shielding section.

Claims (1)

[Claims] 1. A means disposed within a vacuum chamber for receiving bright-field electrons and dark-field electrons transmitted through a sample on the same phosphor screen and converting them into a bright-field optical image and a dark-field optical image, respectively; The light detection means provided therein, and the bright field optical image and the dark field optical image provided through a partition wall that partitions the inside and outside of the vacuum chamber, while maintaining the image positional relationship as they are. an optical fiber plate for transmitting light to a light receiving surface of the light detecting means; and an optical fiber plate disposed outside the vacuum chamber between the optical fiber plate and the light receiving surface of the light detecting means, and detecting the light by the optical fiber plate. A transmission scanning electron microscope characterized by comprising: light shielding means for selectively shielding either the bright field optical image portion or the dark field optical image portion transmitted to the light receiving surface of the means. .